The composition of the products of hydrothermal conversion of a natural concentrate of resin-asphaltene compounds (asphaltite) at temperatures of up to 575 degrees C was studied within the scope of laboratory-scale simulation of trans form at ions of high-molecular-mass components of reservoir oils using the thermal methods of enhanced oil recovery. It was found that thermal degradation takes place in the range 175-575 degrees C, leading to the formation of gases, in particular H2S, and liquid and insoluble products (oil and carbenes-carboids, respectively). The amount of saturated and aromatic compounds in the liquid products of hydrothermal conversion is greater than in the starting sample. The ratio of benzene-extractable to alcohol-benzene-extractable resins substantially varies in favor of the latter compounds, which are enriched in oxygen-containing structural units. The relative amount of higher (> 20 degrees C) n-alkanes in the products of conversion at 175-325 degrees C or 350-575 degrees C is respectively higher or lower than in the virgin asphaltite. At conversion temperatures of >= 400 degrees C, the products contain alpha-olefins.